V60

The NEC V60 (μPD70616) was a CISC processor manufactured by NEC starting in 1986. The V60 was the first 32-bit general-purpose microprocessor commercially available in Japan. A relatively obscure design in the West, it was a radical departure from NEC’s previous V-series CPUs—the NEC V20-V50 series—, which were based on the Intel x86 model, although it retained the ability to emulate them. According to NEC’s documentation, the architectural change was made due to the increasing demand and diversity of programs, calling for a processor with both power (the 32-bit internal bus) and flexibility, having large numbers of general-purpose registers—a common feature of RISC architectures and a benefit to the emerging high-level languages. The V60 architecture retained however CISC features (which its manual describe as mainframe-based) like variable-length instructions, memory-to-memory operations including string manipulation, and fairly complex operand addressing schemes. Although it had a 32-bit internal bus, the V60 had only a 16-bit external data bus and a 24-bit address bus. Its architecture was carried largely intact to the V70 (μPD70632) model, which had external 32-bit buses and was released in 1987. Launched in 1989, the V80 (μPD70832) was the culmination of the series having on-chip caches, a branch predictor, and less reliance on microcode for complex operations. The V60-V80 architecture did not enjoy much commercial success. The operating systems developed for the V60-V80 series were generally oriented toward real-time operation. Having been used in some Japanese game arcade products, the V60 and V70 also survive in emulation software for this niche.